This invention is in the field of belt conveyors and in particular such conveyors for conveying granular material such as grain.
Belt conveyors are commonly used for conveying granular particulate material such as grain, fertilizer, salt and the like from a transport vehicle up and into a storage facility. Commonly there is a hopper at the lower end of the belt conveyor to receive the granular material and direct it onto the belt, which then passes through a tube. The belt makes a transition from a flat orientation coming off the lower roller to a cupped orientation for passage through the tube. The transition can take place between the lower roller and the hopper, in the hopper, or partly in both areas.
Conventionally these belt conveyors include a flashing covering the edges of the belt to substantially prevent the granular material from passing under the belt where same can cause increased friction between the belt and the conveyor parts against which it slides. Such material can build up under the belt and damage it as well. Typically this flashing is only required in the hopper, where the level of granular material often rises above the edges of the belt. Once the belt enters the tube, the granular material is at a level below the edges of the belt and there is little chance of same spilling over the edges.
Belt conveyors have an advantage over the common alternative auger conveyor in that the belt conveyor does not damage certain susceptible material such as peas, lentils and the like. Belt conveyors however have reduced capacity, compared to a similar size auger conveyor. U.S. Pat. No. 5,735,386 to Epp et al. is directed to increasing the capacity of a belt conveyor for granular material by mounting an auger in the hopper to help feed material into the tube.
It is the object of the present invention to provide a belt conveyor for receiving and conveying granular material that has increased capacity over conventional belt conveyors.
It is a further object of the invention to provide such a belt conveyor that is simple and inexpensive to manufacture.
It is a further object of the invention to provide a method of increasing the capacity of those belt conveyors for granular material of the type where the belt is in a cupped orientation while passing through the conveyor hopper.
The invention provides, in one aspect, a belt conveyor for conveying granular material comprising a tube having an upper output end and a lower input end. A hopper for receiving granular material is attached at the input end of the tube, the hopper including a hopper end wall and hopper side walls extending from the end wall to the input end of the tube.
A belt having an upper surface and a lower surface, has an upper path extending from a lower roller, then through a bottom of the hopper, then through the tube to an upper roller and a lower path from the upper roller to the lower roller. A drive moves the belt along the upper path from the input end toward the output end of the tube. Guide members at a lower end of the conveyor guide the belt from a flat orientation as the belt leaves the lower roller into a cupped orientation as the belt enters the hopper. The cupped orientation is maintained by sliding contact at an interface between the lower surface of the belt and the hopper walls as the belt passes through the hopper. Left and right baffle members are attached along the hopper side walls from the end wall substantially to the tube in proximity to left and right edges of the belt. The baffle members extend from the hopper wall approximately to the upper surface of the belt and thereby prevent the granular material from sliding down the hopper walls into contact with the interface between the lower surface of the belt and the hopper walls. The belt has a width that is substantially fully exposed to granular material entering the hopper.
As the belt is cupped while passing through the hopper the edges are oriented upward and the baffle in proximity to the edges prevents granular material from sliding down the hopper wall into contact with the interface where the lower surface of the belt slides against the hopper wall. The granular material sliding down the wall appears to apply enough pressure to the flexible belt edge to cause particles of granular material to work their way under the belt in large enough numbers to cause increased friction and eventual damage to the belt.
The baffle members should be close to the belt edges, however it is not critical that they be so close as to prevent any contact between the interface and granular material. The gap between the baffle member and the edge of the belt can be such that some particles can enter the gap and come into contact with the interface. It is only necessary to prevent direct downward pressure on the interface, such as when granular material piles up over the interface. The baffle member extends from the hopper wall and prevents this pressure from being exerted. The full width of the belt is left exposed, increasing the capacity of the belt conveyor substantially.
The hopper side walls could guide the belt from a first cupped orientation at the hopper end wall to a second cupped orientation at the tube, the belt having the left and right edges thereof closer to each other in the second cupped orientation than in the first cupped orientation. In this manner the cupping of the belt to conform to the tube is accomplished in two stages. First, a relatively abrupt change is made between the lower roller and the end wall, prior to the belt entering the hopper. This change to the first cupped orientation puts the edges of the belt in an upward orientation and allows the baffle members to prevent the granular material in the hopper from contacting the interface where the lower surface of the belt contacts the hopper walls. The change from the first to the second cupped orientation is accomplished by slightly angling the hopper walls. This two stage transition requires a lesser distance between the lower roller and the end wall of the hopper, as a portion of the transition takes place in the hopper. Moving the lower roller closer to the end wall of the hopper reduces interference with trucks and the like dumping into the hopper.
The invention provides, in a second aspect, a method of increasing the capacity of a belt conveyor of the type having a cupped belt running through a hopper with a width of flashing extending from hopper walls over a portion of each side of the belt to prevent granular material from moving under the belt, the method comprising reducing the width of the flashing such that a greater width of the belt is exposed to granular material entering the hopper.
Tests were conducted by the inventors on a belt conveyor operated at an angle of 30 degrees. The belt conveyor had a 1 inch belt and a 10 inch tube, and a conventional flashing covering two inches on each side of the belt. Reducing the flashing coverage to one inch on each side of the belt increased capacity by 30%, while reducing the flashing coverage to zero on each side of the belt increased capacity by 60% over the two inch coverage.
It is apparent that the amount of moving belt exposed to the granular material during loading of the belt for passage up through the tube has a hitherto unrealized significant effect on the capacity of the belt conveyor.